Fertilizers and soil enriching materials are produced in a range of enriching ingredients. Some such products are mainly soil fillers, and others can be classified as fertilizers.
Fertilizers contain percentages of nitrogen, phosphate and potassium, the constituents that plants need most to grow that is lacking in soil. These ingredients are found naturally in manure products, and are created by chemical processed as well although obviously the end product is not organic.
In addition to chemically produced fertilizers and manure products, sewer sludge is also used in a purified form for fertilizer. Different types of mulches represent a fourth group of products used as soil conditioners as well.
All of these products have their strengths and weaknesses. Natural manure fertilizers generally have a bad aroma. Fish emulsion fertilizer is very rich, but probably has the worst smell of any of the fertilizers.
Artificial fertilizers produced by chemical processes do not have offending odors, but may burn the plants they are intended to fertilize and do not appeal to many people who insist on having organic fertilizers.
Sewer sludge may not have a terribly offending odor considering its source, but the idea of using sewer sludge in a garden repels some people. This may be for good reason, inasmuch as there may be traces of heavy metals, or other toxic substances in sludge.
Organic fertilizers that are rich in the natural ingredients that fertilizers need, but do not have an offending aroma, are few and far between.